The present invention relates to a lock and key combination including a cylinder lock and a key with a flat key blade. The lock has a rotatable key plug having a key slot for receiving a flat key blade, and at least two side locking tumblers in the cylinder lock, said side locking tumblers being guided for elevational and possibly also rotational movement in associated chambers in said key plug and having transverse fingers projecting into the key slot for engagement with the key blade, upon inserting the key into the key slot. The key blade has an associated code pattern in a side recess for engagement with said side locking tumblers and positioning said side locking tumblers into positions that allow the key plug to rotate in the cylinder lock upon inserting a correctly coded key into the key slot.
Such locks and keys are previously known, e.g. from the U.S. Pat. Nos. 4,756,177 and 5,715,717 (both in the name of Bo Widén). These known lock and key systems provide a high level of security and offer a large number of code combinations.